Proton‐Conductive 3D LnIII Metal–Organic Frameworks for Formic Acid Impedance Sensing

Metal‐organic frameworks (MOFs) as new classes of proton‐conducting materials have been highlighted in recent years. Nevertheless, the exploration of proton‐conducting MOFs as formic acid sensors is extremely lacking. Herein, we prepared two highly stable 3D isostructural lanthanide(III) MOFs, {(M(μ₃‐HPhIDC)(μ₂‐C₂O₄)_0.5(H₂O))?2 H₂O}_n (M=Tb ( ZZU‐1 ); Eu ( ZZU‐2 )) (H₃PhIDC=2‐phenyl‐1H‐imidazole‐4,5‐dicarboxylic acid), in which the coordinated and uncoordinated water molecules and uncoordinated imidazole N atoms play decisive roles for the high‐performance proton conduction and recognition ability for formic acid. Both ZZU‐1 and ZZU‐2 show temperature‐ and humidity‐dependent proton‐conducting characteristics with high conductivities of 8.95×10^?4 and 4.63×10^?4 S cm^‐1 at 98 % RH and 100 °C, respectively. Importantly, the impedance values of the two MOF‐based sensors decrease upon exposure to formic acid vapor generated from formic aqueous solutions at 25 °C with good reproducibility. By comparing the changes of impedance values, we can indirectly determine the concentration of HCOOH in aqueous solution. The results showed that the lowest detectable concentrations of formic acid aqueous solutions are 1.2×10^?2 mol L^?1 by ZZU‐1 and 2.0×10^?2 mol L^?1 by ZZU‐2 . Furthermore, the two sensors can distinguish formic acid vapor from interfering vapors including MeOH, N‐hexane, benzene, toluene, EtOH, acetone, acetic acid and butane. Our research provides a new platform of proton‐conductive MOFs‐based sensors for detecting formic acid.     

Controllable Syntheses of Porous Metal–Organic Frameworks: Encapsulation of LnIII Cations for Tunable Luminescence and Small Drug Molecules for Efficient Delivery

Two porous metal–organic frameworks (MOFs), [Zn₃(L)(H₂O)₂] ? 3 DMF ? 7 H₂O ( MOF‐1 ) and [(CH₃)₂NH₂]₆[Ni₃(L)₂(H₂O)₆] ? 3 DMF ? 15 H₂O ( MOF‐2 ), were synthesized solvothermally (H₆L=1,2,3,4,5,6‐hexakis(3‐carboxyphenyloxymethylene)benzene). In MOF ‐ 1 , neighboring Zn^II trimers are linked by the backbones of L ligands to form a fascinating 3D six‐connected framework with the point symbol (4¹².6³) (4¹².6³). In MOF‐2 , eight L ligands bridge six Ni^II atoms to generate a rhombic‐dodecahedral [Ni₆L₈] cage. Each cage is surrounded by eight adjacent ones through sharing of carboxylate groups to yield an unusual 3D porous framework. Encapsulation of Ln^III cations for tunable luminescence and small drug molecules for efficient delivery were investigated in detail for MOF‐1 .     

Solvent‐Vapor‐Induced Reversible Single‐Crystal‐to‐Single‐Crystal Transformation of a Triphosphaazatriangulene‐Based Metal–Organic Framework

A triphosphaazatriangulene (H₃L) was synthesized through an intramolecular triple phospha‐Friedel–Crafts reaction. The H₃L triangulene contains three phosphinate groups and an extended π‐conjugated framework, which enables the stimuli‐responsive reversible transformation of [Cu(HL)(DMSO)?(MeOH)]_n, a 3D‐MOF that exhibits reversible sorption characteristics, into (H₃L?0.5 [Cu₂(OH)₄?6 H₂O] ?4 H₂O), a 1D‐columnar assembled proton‐conducting material. The hydrophilic nature of the latter resulted in a proton conductivity of 5.5×10^?3 S cm^?1 at 95 % relative humidity and 60 °C.     

Water‐Mediated Proton Conduction in a Robust Triazolyl Phosphonate Metal–Organic Framework with Hydrophilic Nanochannels

The development of water‐mediated proton‐conducting materials operating above 100 °C remains challenging because the extended structures of existing materials usually deteriorate at high temperatures. A new triazolyl phosphonate metal–organic framework (MOF) [La₃ L ₄(H₂O)₆]Cl ? x H₂O ( 1 , L ^2?=4‐(4H‐1,2,4‐triazol‐4‐yl)phenyl phosphonate) with highly hydrophilic 1D channels was synthesized hydrothermally. Compound 1 is an example of a phosphonate MOF with large regular pores with 1.9 nm in diameter. It forms a water‐stable, porous structure that can be reversibly hydrated and dehydrated. The proton‐conducting properties of 1 were investigated by impedance spectroscopy. Magic‐angle spinning (MAS) and pulse field gradient (PFG) NMR spectroscopies confirm the dynamic nature of the incorporated water molecules. The diffusivities, determined by PFG NMR and IR microscopy, were found to be close to that of liquid water. This porous framework accomplishes the challenges of water stability and proton conduction even at 110 °C. The conductivity in 1 is proposed to occur by the vehicle mechanism.     

Two new NiII and ZnII metal–organic frameworks of glutarate and 1,4‐bis[(2‐methyl‐1H‐imidazol‐1‐yl)methyl]benzene ligands: syntheses,structures and luminescence sensing properties

Two new metal–organic frameworks (MOFs), namely, three‐dimensional poly[diaquabis{μ₂‐1,4‐bis[(2‐methyl‐1H‐imidazol‐1‐yl)methyl]benzene}bis(μ₂‐glutarato)dinickel(II)] monohydrate], {[Ni₂(C₅H₆O₄)₂(C₁₆H₁₈N₄)₂(H₂O)₂]·H₂O}_n or {[Ni₂(Glu)₂(1,4‐mbix)₂(H₂O)₂]·H₂O}_n, ( I ), and two‐dimensional poly[[{μ₂‐1,4‐bis[(2‐methyl‐1H‐imidazol‐1‐yl)methyl]benzene}(μ₂‐glutarato)zinc(II)] tetrahydrate], {[Zn(C₅H₆O₄)(C₁₆H₁₈N₄)]·4H₂O}_n or {[Zn(Glu)(1,4‐mbix)]·4H₂O}_n ( II ), have been synthesized hydrothermally using glutarate (Glu^2?) mixed with 1,4‐bis[(2‐methyl‐1H‐imidazol‐1‐yl)methyl]benzene (1,4‐mbix), and characterized by single‐crystal X‐ray diffraction, IR and UV–Vis spectroscopy, powder X‐ray diffraction, and thermogravimetric and photoluminescence analyses. Ni^II MOF ( I ) shows a 4‐connected 3D framework with point symbol 6⁶, but is not a typical dia network. Zn^II MOF ( II ) displays a two‐dimensional 4⁴‐ sql network with one‐dimensional water chains penetrating the grids along the c direction. The solid‐state photoluminescence analysis of ( II ) was performed at room temperature and the MOF exhibits highly selective sensing toward Fe³⁺ and Cr₂O₇^2? ions in aqueous solution.     

The Uncommon Channel‐Based Ln‐MOFs for Highly Selective Fe3+ Detection and Superior Rhodamine B Adsorption

Two new isostructural 3D lanthanide–organic frameworks [H₂N(Me)₂] [Ln₃(OH)(bpt)₃(H₂O)₃] (DMF)₂?(H₂O)₄ ( 1‐Ln ; Ln=Sm and Eu) with a 1D channel (25 Å) have been successfully assembled from the rare trinuclear [Ln₃(OH)(COO)₉] clusters and biphenyl‐3,4′,5‐tricarboxylic acid (H₃bpt) and exhibit high stability towards water in the pH range 3–10. MOF 1‐Eu is a promising luminescent probe for sensing Fe³⁺ in aqueous solution and is also selective towards rhodamine B (RhB) with a superior adsorption capacity of 735 mg g^?1, which is the highest among the reported Ln‐MOFs for RhB removal so far. Periodic DFT calculations further confirmed the selective adsorption of rhodamine B over other dyes.     

Metal–Organic Frameworks Containing Missing‐Linker Defects Leading to High Hydroxide‐Ion Conductivity

The ionic conductivity properties of the face‐centered cubic [Ni₈(OH)₄(H₂O)₂(BDP_X)₆] (H₂BDP_X=1,4‐bis(pyrazol‐4‐yl)benzene‐4‐X with X=H ( 1 ), OH ( 2 ), NH₂ ( 3 )) metal–organic framework (MOF) systems as well as their post‐synthetically modified materials K[Ni₈(OH)₅(EtO)(BDP_X)_5.5] ( 1@KOH , 3@KOH ) and K₃[Ni₈(OH)₃(EtO)(BDP_O)₅] ( 2@KOH ), which contain missing‐linker defects, have been studied by variable temperature AC impedance spectroscopy. It should be noted that these modified materials exhibit up to four orders of magnitude increase in conductivity ^‐values in comparison to pristine 1 – 3 systems. As an example, the conductivity value of 5.86×10^?9 S cm^?1 (activation energy E_a of 0.60 eV) for 2 at 313 K and 22 % relative humidity (RH) increases up to 2.75×10^?5 S cm^?1 (E_a of 0.40 eV) for 2@KOH . Moreover, a further increase of conductivity values up to 1.16×10^?2 S cm^?1 and diminution of E_a down to 0.20 eV is achieved at 100 % RH for 2@KOH . The increased porosity, basicity and hydrophilicity of the 1@KOH – 3@KOH materials compared to the pristine 1 – 3 systems should explain the better performance of the KOH‐modified materials.     

Water‐stable Adenine‐based MOFs with Polar Pores for Selective CO2 Capture

Here, we report two novel water‐stable amine‐functionalized MOFs, namely IISERP‐MOF26 ([NH₂(CH₃)₂][Cu₂O(Ad)(BDC)]?(H₂O)₂(DMA), 1 ) and IISERP‐MOF27 ([NH₂(CH₃)₂]_1/2[Zn₄O(Ad)₃(BDC)₂]?(H₂O)₂(DMF)_1/2, 2 ), which show selective CO₂ capture capabilities. They are made by combining inexpensive and readily available terephthalic acid and N‐rich adenine with Cu and Zn, respectively. They possess 1D channels decorated by the free amine group from the adenine and the polarizing oxygen atoms from the terephthalate units. Even more, there are dimethyl ammonium (DMA⁺) cations in the pore rendering an electrostatic environment within the channels. The activated Cu‐ and Zn‐MOFs physisorb about 2.7 and 2.2 mmol g^?1 of CO₂, respectively, with high CO₂/N₂ and moderate CO₂/CH₄ selectivity. The calculated heat of adsorption (HOA=21–23 kJ mol^?1) for the CO₂ in both MOFs suggest optimal physical interactions which corroborate well with their facile on‐off cycling of CO₂. Notably, both MOFs retain their crystallinity and porosity even after soaking in water for 24 hours as well as upon exposure to steam over 24 hours. The exceptional thermal and chemical stability, favorable CO₂ uptakes and selectivity and low HOA make these MOFs promising sorbents for selective CO₂ capture applications. However, the MOF′s low heat of adsorption despite having a highly CO₂‐loving groups lined walls is quite intriguing.     

Three novel topologically different metal–organic frameworks built from 3‐nitro‐4‐(pyridin‐4‐yl)benzoic acid

The design and synthesis of metal–organic frameworks (MOFs) have attracted much interest due to the intriguing diversity of their architectures and topologies. However, building MOFs with different topological structures from the same ligand is still a challenge. Using 3‐nitro‐4‐(pyridin‐4‐yl)benzoic acid (HL) as a new ligand, three novel MOFs, namely poly[[(N,N‐dimethylformamide‐κO)bis[μ₂‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ³O,O′:N]cadmium(II)] N,N‐dimethylformamide monosolvate methanol monosolvate], {[Cd(C₁₂H₇N₂O₄)₂(C₃H₇NO)]·C₃H₇NO·CH₃OH}_n, ( 1 ), poly[[(μ₂‐acetato‐κ²O:O′)[μ₃‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ³O:O′:N]bis[μ₃‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ⁴O,O′:O′:N]dicadmium(II)] N,N‐dimethylacetamide disolvate monohydrate], {[Cd₂(C₁₂H₇N₂O₄)₃(CH₃CO₂)]·2C₄H₉NO·H₂O}_n, ( 2 ), and catena‐poly[[[diaquanickel(II)]‐bis[μ₂‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ²O:N]] N,N‐dimethylacetamide disolvate], {[Ni(C₁₂H₇N₂O₄)₂(H₂O)₂]·2C₄H₉NO}_n, ( 3 ), have been prepared. Single‐crystal structure analysis shows that the Cd^II atom in MOF ( 1 ) has a distorted pentagonal bipyramidal [CdN₂O₅] coordination geometry. The [CdN₂O₅] units as 4‐connected nodes are interconnected by L^? ligands to form a fourfold interpenetrating three‐dimensional (3D) framework with a dia topology. In MOF ( 2 ), there are two crystallographically different Cd^II ions showing a distorted pentagonal bipyramidal [CdNO₆] and a distorted octahedral [CdN₂O₄] coordination geometry, respectively. Two Cd^II ions are connected by three carboxylate groups to form a binuclear [Cd₂(COO)₃] cluster. Each binuclear cluster as a 6‐connected node is further linked by acetate groups and L^? ligands to produce a non‐interpenetrating 3D framework with a pcu topology. MOF ( 3 ) contains two crystallographically distinct Ni^II ions on special positions. Each Ni^II ion adopts an elongated octahedral [NiN₂O₄] geometry. Each Ni^II ion as a 4‐connected node is linked by L^? ligands to generate a two‐dimensional network with an sql topology, which is further stabilized by two types of intermolecular OW—HW…O hydrogen bonds to form a 3D supramolecular framework. MOFs ( 1 )–( 3 ) were also characterized by powder X‐ray diffraction, IR spectroscopy and thermogravimetic analysis. Furthermore, the solid‐state photoluminescence of HL and MOFs ( 1 ) and ( 2 ) have been investigated. The photoluminescence of MOFs ( 1 ) and ( 2 ) are enhanced and red‐shifted with respect to free HL. The gas adsorption investigation of MOF ( 2 ) indicates a good separation selectivity (71) of CO₂/N₂ at 273 K (i.e. the amount of CO₂ adsorption is 71 times higher than N₂ at the same pressure).     

Cu3(hexaiminotriphenylene)2: An Electrically Conductive 2D Metal–Organic Framework for Chemiresistive Sensing

The utility of metal–organic frameworks (MOFs) as functional materials in electronic devices has been limited to date by a lack of MOFs that display high electrical conductivity. Here, we report the synthesis of a new electrically conductive 2D MOF, Cu₃(HITP)₂ (HITP=2,3,6,7,10,11‐hexaiminotriphenylene), which displays a bulk conductivity of 0.2 S cm^?1 (pellet, two‐point‐probe). Devices synthesized by simple drop casting of Cu₃(HITP)₂ dispersions function as reversible chemiresistive sensors, capable of detecting sub‐ppm levels of ammonia vapor. Comparison with the isostructural 2D MOF Ni₃(HITP)₂ shows that the copper sites are critical for ammonia sensing, indicating that rational design/synthesis can be used to tune the functional properties of conductive MOFs.     

Cooperative Cluster Metalation and Ligand Migration in Zirconium Metal–Organic Frameworks

Cooperative cluster metalation and ligand migration were performed on a Zr‐MOF, leading to the isolation of unique bimetallic MOFs based on decanuclear Zr₆M₄ (M=Ni, Co) clusters. The M²⁺ reacts with the μ₃‐OH and terminal H₂O ligands on an 8‐connected [Zr₆O₄(OH)₈(H₂O)₄] cluster to form a bimetallic [Zr₆M₄O₈(OH)₈(H₂O)₈] cluster. Along with the metalation of Zr₆ cluster, ligand migration is observed in which a Zr–carboxylate bond dissociates to form a M–carboxylate bond. Single‐crystal to single‐crystal transformation is realized so that snapshots for cooperative cluster metalation and ligand migration processes are captured by successive single‐crystal X‐ray structures. In³⁺ was metalated into the same Zr‐MOF which showed excellent catalytic activity in the acetaldehyde cyclotrimerization reaction. This work not only provides a powerful tool to functionalize Zr‐MOFs with other metals, but also structurally elucidates the formation mechanism of the resulting heterometallic MOFs.     

Crystal Structures and Proton Conductivities of a MOF and Two POM–MOF Composites Based on CuII Ions and 2,2′‐Bipyridyl‐3,3′‐dicarboxylic Acid

We have succeeded in constructing a metal–organic framework (MOF), [Cu(bpdc)(H₂O)₂]_n (H₂bpdc=2,2′‐bipyridyl‐3,3′‐dicarboxylic acid, 1 ), and two poly‐POM–MOFs (POM=polyoxometalate), {H[Cu(Hbpdc)(H₂O)₂]₂[PM₁₂O₄₀] ? n H₂O}_n (M=Mo for 2 , W for 3 ), by the controllable self‐assembly of H₂bpdc, Keggin‐anions, and Cu²⁺ ions based on electrostatic and coordination interactions. Notably, these three compounds all crystallized in the monoclinic space group P2₁/n, and the Hbpdc^? and bpdc^2? ions have the same coordination mode. Interestingly, in compounds 2 and 3 , Hbpdc^? and the Keggin‐anion are covalently linked to the transition metal copper at the same time as polydentate organic ligand and as polydentate inorganic ligand, respectively. Complexes 2 and 3 represent new and rare examples of introducing the metal N‐heterocyclic multi‐carboxylic acid frameworks into POMs, thereby, opening a pathway for the design and the synthesis of multifunctional hybrid materials based on two building units. The Keggin‐anions being immobilized as part of the metal N‐heterocyclic multi‐carboxylic acid frameworks not only enhance the thermal stability of compounds 2 and 3 , but also introduce functionality inside their structures, thereby, realizing four approaches in the 1D hydrophilic channel used to engender proton conductivity in MOFs for the first time. Complexes 2 and 3 exhibit good proton conductivity (10^?4 to ca. 10^?3 S cm^?1) at 100 °C in the relative humidity range 35 to about 98 %.     

Hydrogen‐Bonded Organic Frameworks (HOFs): A New Class of Porous Crystalline Proton‐Conducting Materials

Two porous hydrogen‐bonded organic frameworks (HOFs) based on arene sulfonates and guanidinium ions are reported. As a result of the presence of ionic backbones appended with protonic source, the compounds exhibit ultra‐high proton conduction values (σ) 0.75× 10^?2 S cm^?1 and 1.8×10^?2 S cm^?1 under humidified conditions. Also, they have very low activation energy values and the highest proton conductivity at ambient conditions (low humidity and at moderate temperature) among porous crystalline materials, such as metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). These values are not only comparable to the conventionally used proton exchange membranes, such as Nafion used in fuel cell technologies, but is also the highest value reported in organic‐based porous architectures. Notably, this report inaugurates the usage of crystalline hydrogen‐bonded porous organic frameworks as solid‐state proton conducting materials.     

Fabrication of Crystalline Microporous Membrane from 2D MOF Nanosheets for Gas Separation

Metal‐organic frameworks (MOFs)‐based membranes have shown great potentials as applications in gas separation. In this work, a uniform membrane based on 2D MOF Ni₃(HITP)₂ (HITP=2,3,6,7,10,11‐hexaaminotriphenylene) was fabricated on ordered macroporous AAO via the filtration method. To fabricate the membrane, we obtained the Ni₃(HITP)₂ nanosheets as building blocks via a soft‐physical exfoliation method successfully that were confirmed by AFM and TEM. We also studied the H₂, CO₂ and N₂ adsorption isotherms of Ni₃(HITP)₂ powder at room temperature, which shows Ni₃(HITP)₂ has high heats of adsorption for CO₂ and high selectivity of CO₂ over N₂. Gas permeation tests indicate that the Ni₃(HITP)₂ membrane shows high permeance and selectivity of CO₂ over N₂, as well as good selectivity of H₂ over N₂. The ideal separation factors of CO₂/N₂ and H₂/N₂ from sing‐gas permeances are 13.6 and 7.8 respectively, with CO₂ permeance of 3.15×10^?6 mol?m^?2?s^?1?Pa^?1. The membrane also showed good stability, durability and reproducibility, which are of potential interest for practical applications in the CO₂ separations.     

Two Highly Stable Proton Conductive Cobalt(II)–Organic Frameworks as Impedance Sensors for Formic Acid

Metal–organic frameworks (MOFs) have been extensively explored as advanced chemical sensors in recent years. However, there are few studies on MOFs as acidic gas sensors, especially proton conductive MOFs. In this work, two new proton-conducting 3D MOFs, {[Co₃(p-CPhHIDC)₂(4,4′-bipy)(H₂O)] ⋅ 2 H₂O}_n ( 1 ) (p-CPhH₄IDC=2-(4-carboxylphenyl)-1 H-imidazole-4,5-dicarboxylic acid; 4,4′-bipy=4,4′-bipyridine) and {[Co₃(p-CPhHIDC)₂(bpe)(H₂O)] ⋅ 3 H₂O}_n ( 2 ) (bpe=trans-1,2-bis(4-pyridyl)ethylene) have been solvothermally prepared and investigated their formic acid sensing properties. Both MOFs 1 and 2 show temperature- and humidity-dependent proton conductive properties and exhibit optimized proton conductivities of 1.04×10⁻³ and 7.02×10⁻⁴ S cm at 98 % relative humidity (RH) and 100 °C, respectively. The large number of uncoordinated carboxylic acid sites, free and coordination water molecules, and hydrogen-bonding networks inside the frameworks are favorable to the proton transfer. By measuring the impedance values after exposure to formic acid vapor at 98 % or 68 % RH and 25 °C, both MOFs indicate reproducibly high sensitivity to the analyte. The detection limit of formic acid vapor is as low as 35 ppm for 1 and 70 ppm for 2 . Meanwhile, both MOFs also show commendable selectivity towards formic acid among interfering solutions. The proton conducting and formic acid sensing mechanisms have been suggested according to the structural analysis, E_a calculations, N₂ and water vapor absorptions, PXRD and SEM measurements. This work will open a new avenue for proton-conductive MOF-based impedance sensors and promote the potential application of these MOFs for indirectly monitoring the concentrations of formic acid vapors.     

Studies on the nuclease activity and interactions of the mixed‐polypyridyl [Ni2(1,3‐tpbd)(diimine)2(H2O)2]4+ complexes with thioredoxin reductase

Three new nickel(II) complexes formulated as [Ni₂(1,3‐tpbd)(diimine)₂(H₂O)₂]⁴⁺ [1,3‐tpbd = N,N,N′,N′‐tetrakis(2‐pyridylmethyl)benzene‐1,3‐diamine, where diimine is an N,N‐donor heterocyclic base like 1,10‐phenanthroline (phen),2,2′‐bipyridine (bpy), 4,5‐diazafluoren‐9‐one (dafo)], have been synthesized and structurally characterized by X‐ray crystallography: [Ni₂(1,3‐tpbd)(phen)₂(H₂O)₂]⁴⁺ (1), [Ni₂(1,3‐tpbd)(bpy)₂(H₂O)₂]⁴⁺(2) and [Ni₂(1,3‐tpbd)(dafo)₂(H₂O)₂]⁴⁺ (3). Single‐crystal diffraction reveals that the metal atoms in the complexes are all in a distorted octahedral geometry and in a trans arrangement around 1,3‐tpbd ligand. The interactions of the three complexes with calf thymus DNA (CT‐DNA) have been investigated by UV absorption, fluorescence spectroscopy, circular dichroism and viscosity. The apparent binding constant (K_app) values are calculated to be 1.91 × 10⁵ m ^?1 for 1, 1.18 × 10⁵ m ^?1 for 2, and 1.35 × 10⁵ m ^?1 for 3, following the order 1 > 3 > 2. The higher DNA binding affinity of 1 is due to the involvement in partial insertion of the phen ring between the DNA base pairs. A decrease in relative viscosities of DNA upon binding to 1–3 is consistent with the DNA binding affinities. These complexes efficiently display oxidative cleavage of supercoiled DNA in the presence of H₂O₂ (250 µ m ), with 3 exhibiting the highest nuclease activity. The rate constants for the conversion of supercoiled to nicked DNA are 5.28 × 10^?5 s^?1 (for 1), 6.67 × 10^?5 s^?1 (for 2) and 1.39 × 10^?4 s^?1 (for 3), also indicating that complex 3 shows higher catalytic activity than 1 and 2. Here the nuclease activity is not readily correlated to binding affinity. The inhibitory effect of complexes 1–3 on thioredoxin reductase has also been examined. The IC₅₀ values are calculated to be 26.54 ± 0.57, 31.03 ± 3.33 and 8.69 ± 2.54 µ m , respectively, showing a more marked inhibitory effect on thioredoxin reductase by complex 3 than the other two complexes. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and Structural Characterization of a Binuclear Mixed‐Ligand (Salicylate and N,N‐diethylnicotinamide) Nickel(II) Complex,Its Magnetic Properties. [Ni2(µ‐Sal)4(Dena)2]H2O

The title complex of [Ni₂(µ‐Sal)₄(Dena)₂]H₂O, [( µ‐tetrakissalicylato‐κ‐O,O)(bis‐N,N‐diethylnicotinamide‐κ‐N)(binickel(II))]hydrate, C₄₈H₅₂Ni₂N₄O₁₆, has been synthesized and explained as structural using some elemental analysis, FT‐IR spectra, UV‐Vis reflectance, magnetic measurements, thermal analysis and x‐ray diffraction methods. The analysis results showed that the unit cell of complex includes two molecules Ni^II cation, four molecules salicylates as bridge and two molecules N,N‐diethylnicotinamide ligands, also there is one molecule hydrated aqua. The compound crystallizes in the monoclinic space group P2₁/c with the following unit‐cell parameters: a =13.6776(6) Å, b =10.5238(3) Å, c =21.8165(9), α=90.00°, β=126.546(3)°, γ=90.00º and Z=2. The compound [Ni₂(µ‐Sal)₄(Dena)₂]H₂O is a typical paddle‐wheel complex structure. Two Ni^II ions are bridged by four salicylate ligands (O2, O2ⁱ, O3, O3ⁱ, O5, O5ⁱ, O6 and O6ⁱ) using a µ‐COO^? coordination mode [symmetry code: (i) 1‐x, 1‐y, 1‐z]. Each Ni^II also coordinates to one nitrogen atom (N1 and N1ⁱ) from one N,N‐diethylnicotinamide ligand molecule in the axial position. The complex has strong paramagnetic properties.     

Assembly of Three 2D Metal‐Organic Frameworks (MOFs) Derived from Flexible Ligands, 1,4‐bis(3‐pyridyl)‐2,3‐diaza‐1,3‐butadiene (3‐bpd) and/or 1,2‐bis(4‐pyridyl)ethane (dpe)

Three coordination polymers, {[Cd(3‐bpd)₂(NCS)₂]×C₂H₅OH}_n ( 1 ), {[Cd(3‐bpd)(dpe)(NO₃)₂]×(3‐bpd)}₂ ( 2 ), {[Cd(dpe)₂(NCS)₂]×3‐bpd×2H₂O}_n ( 3 ) (3‐bpd = 1,4‐bis(3‐pyridyl)‐2,3‐diaza‐1,3‐butadiene; dpe = 1,2‐bis(4‐pyridyl)ethane), were prepared and structurally characterized by a single‐crystal X‐ray diffraction method. In compound 1 , each Cd(II) ion is six‐coordinate bonded to six nitrogen atoms from four 3‐bpd and two NCS^? ligands. The 3‐bpd acts as a bridging ligand connecting the Cd(II) ion to generate a 2D layered metal‐organic framework (MOF) by using a rhomboidal‐grid as the basic building units with the 4⁴ topology. In compound 2 , the Cd(II) ion is also six‐coordinate bonded to four nitrogen atoms of two 3‐bpd, two dpe and two oxygen atoms of two NO₃^? ligands. The 3‐bpd and dpe ligands both adopt bis‐monodentate coordination mode connecting the Cd(II) ions to generate a 2D layered MOF by using a rectangle‐grid as the basic building units with the 4⁴ topology. In compound 3 , two crystallographically independent Cd(II) ions are both coordinated by four nitrogen atoms of dpe ligands in the basal plane and two nitrogen atom of NCS^? in the axial sites. The dpe acts as a bridging ligand to connect the Cd(II) ions forming a 2D interpenetrating MOFs by using a square‐grid as the basic unit with the 4⁴ topology. All of their 2D layered MOFs in compounds 1 ‐ 3 are then arranged in a parallel non‐interpenetrating ABAB—packing manner in 1 and 2 , and mutually interpenetrating manner in 3 , respectively, to extend their 3D supramolecular architectures with their 1D pores intercalated with solvent (ethanol in 1 or H₂O in 3 ) or free 3‐bpd molecules in 2 and 3 , respectively. The photoluminescence measurements of 1 ‐ 3 reveal that the emission is tentatively assigned to originate from π‐π* transition for 1 and 2 and probably due to ligand‐center luminescence for compounds 3 , respectively.     

Polycarboxylate‐Templated Coordination Polymers: Role of Templates for Superprotonic Conductivities of up to 10−1 S cm−1

Three coordination polymers (CPs) have been synthesized based on a [Co(bpy)(H₂O)₄]²⁺ chain (bpy=4,4′‐bipyridine) by a template approach. The frameworks are neutralized by different templated polycarboxylate anions (furan di‐carboxylate (fdc) in Co‐fdc, benzene tri‐carboxylate (btc) in Co‐tri and benzene tetra‐carboxylate (btec) in Co‐tetra). These templates with different degrees of protonation and ionic carrier concentration played significant role on crystal packing as well as formation of well‐directed H‐bonded networks which made these CPs perform well in proton conduction (PC). The PC value reaches to 1.49×10^?1 S cm^?1 under 80 °C and 98 % relative humidity (R.H.) for Co‐tri, which is the highest among CPs/MOFs/COFs and is an example of conductivity in the order of 10^?1 S cm^?1. Co‐tri and Co‐tetra are excellent proton conductors at mild temperature (40 °C) and 98 % R.H. (conductivities up to 2.92×10^?2 and 1.38×10^?2 S cm^?1, respectively).     

Boosting Proton Conductivity in Highly Robust 3D Inorganic Cationic Extended Frameworks through Ion Exchange with Dihydrogen Phosphate Anions

The limited long‐term hydrolytic stability of rapidly emerging 3D‐extended framework materials (MOFs, COFs, MOPs, etc.) is still one of major barriers for their practical applications as new solid‐state electrolytes in fuel cells. To obtain hydrolytically stable materials, two H₂PO₄^?‐exchanged 3D inorganic cationic extended frameworks (CEFs) were successfully prepared by a facile anion‐exchange method. Both anion‐exchanged CEFs (YbO(OH)P and NDTBP) show significantly enhanced proton conductivity when compared with the original materials (YbO(OH)Cl and NDTB) with an increase of up to four orders‐of‐magnitude, reaching 2.36×10^?3 and 1.96×10^?2 S cm^?1 at 98 % RH and 85 °C for YbO(OH)P and NDTBP, respectively. These values are comparable to the most efficient proton‐conducting MOFs. In addition, these two anion‐exchanged materials are stable in boiling water, which originates from the strong electrostatic interaction between the H₂PO₄^? anion and the cationic host framework, showing a clear advance over all the acid‐impregnated materials (H₂SO₄@MIL‐101, H₃PO₄@MIL‐101, and H₃PO₄@Tp‐Azo) as practical solid‐state fuel‐cell electrolytes. This work offers a new general and efficient approach to functionalize 3D‐extended frameworks through an anion‐exchange process and achieves water‐stability with ultra‐high proton conductivity above 10^?2 S cm^?1.